Heterothermy

Heterothermy is a thermoregulatory pattern in which an animal’s body temperature varies over time or between regions of its body. It contrasts with maintaining a uniformly stable body temperature.

Torpor: A reversible state of reduced metabolism and body temperature that conserves energy. Torpor produces pronounced, temporary heterothermy by lowering body temperature.
Thermoregulation: The processes by which organisms control heat exchange and body temperature. Heterothermy is one pattern of thermoregulation, rather than a separate kind of heat exchange.
Arctic ground squirrel: A ground squirrel species that hibernates in the Arctic and tolerates very low body temperatures. Its hibernation demonstrates extreme seasonal heterothermy in a mammal.
Metabolic rate: The rate at which an organism uses energy through metabolism. Lowering body temperature typically reduces metabolic demand during torpor.
Hibernation: A seasonal pattern of prolonged torpor interrupted by periodic arousals. Its repeated deep cooling and rewarming is a classic temporal form of heterothermy.
Endothermy: Regulation of body temperature primarily through heat generated by metabolism. Endotherms can still vary their body temperatures and therefore can be heterothermic.
Hummingbird: A small bird capable of entering nightly torpor to reduce energy expenditure. Nightly cooling lets hummingbirds conserve energy when food and warmth are limited.
Q10 temperature coefficient: A measure of how much a biological rate changes with a 10-degree temperature shift. It describes why cooling slows many physiological processes during heterothermy.
Daily torpor: A short bout of torpor, usually lasting hours and recurring within a daily cycle. It shows how heterothermy can occur on a daily rather than seasonal timescale.
Ectothermy: Dependence on external heat sources for most body warming. Ectothermy concerns heat sources, whereas heterothermy describes temperature variation.

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